Tailboom-stabilized vtol aircraft

ABSTRACT

A disclosed flying craft includes a suspension structure having a first end and a second end, a lift unit, and a payload unit. The lift unit includes a nacelle and a tailboom, and pivotally couples to the first end of the suspension structure, and a payload unit couples to the structure&#39;s second end. Thus the tailboom can pivotally couple with respect to the payload unit, which advantageously permits the tailboom to assume an orientation desirable for a particular mode of flight. During vertical flight or hover, the tailboom can hang from the lift unit in an orientation that is substantially parallel to the suspension structure and that minimizes resistance to downwash from the lift unit. During horizontal flight, the tailboom can be orthogonal to the suspension structure, extending rearward in an orientation where it can develop pitching and yawing moments to control and stabilize horizontal flight. Advantageous variations and methods are also disclosed.

BACKGROUND OF THE INVENTION

Vertical Takeoff and Landing (VTOL) aircraft have long been considereddesirable because of their ability to hover in flight and transition inand out of flight without a runway, in addition to flying in ahorizontal direction. The aircraft's lift unit or units have propulsors(e.g., rotor, tiltable jet engines) that develop an aggregate aerialmotive force. This aerial motive force can be viewed as the combinationof a vertical (i.e., countering gravity) and horizontal (i.e., parallelto ground) vector passing through a single point herein called the“center of lift.” For a VTOL aircraft to be stable and controllable inhover or vertical flight, the vertical vector of its aerial motive forcemust pass through its center of mass.

Conventional single-rotor helicopters satisfy this requirement by havingtheir center of mass directly below the rotor. (The number of rotors istypically considered the number of rotor axes, irrespective of whether agiven “rotor” contains a single set of blades or a pair ofcounter-rotating sets.) However, that configuration prevents such anaircraft from tilting its rotor for axial flow in horizontal flight withlift developed by a fixed wing. Instead, it must rely on the rotor's owninefficient lift in edgewise airflow, with only enough rotor clearanceavailable for a slight tilt to develop some horizontal airspeed.

As a compromise, aircraft have been developed that include tiltablerotors on opposite wingtips. This configuration has significantdrawbacks, perhaps primarily that the prospect of blade interferencewith a centerline fuselage limits the diameter of paired co-planarrotors to less than half that of a comparable single rotor. The use ofpaired smaller diameter rotors hurts efficiency, resulting in a hoveringpropulsive force that is less than 70% of what a single rotor wouldproduce for comparable engine power, but with over 40% greater downwashvelocity.

Accordingly, it would be desirable to have a VTOL aircraft that couldemploy a single rotor for stable vertical flight and hover as well asefficient axial airflow in horizontal flight with lift provided by afixed wing. It would also be desirable to have a VTOL aircraft,regardless of the type of lift unit employed, with improved control overtransition between horizontal flight and vertical or hovering flight.

SUMMARY OF THE INVENTION

A flying craft according to various aspects of the present inventionincludes a substantially rigid suspension structure having a first endand a second end, a lift unit, and a payload unit. The lift unitincludes a nacelle (typically housing one or more engines) and atailboom, and pivotally couples to the first end of the suspensionstructure. A payload unit couples to the structure's second end. Thusthe tailboom can pivotally couple with respect to the payload unit,which advantageously permits the tailboom to assume an orientationdesirable for a particular mode of flight.

According to a particularly advantageous aspect of the invention, thelift unit can employ a rotor as a propulsion subsystem to provide anaerial motive force. In a mode of flight where such force ispredominantly countering gravity (vertical flight or hover), thetailboom can hang from the lift unit in an orientation substantiallyparallel to the suspension structure and minimizing resistance todownwash from the lift unit. During a mode of flight in which the rotor(or other suitable propulsion subsystem) provides an aerial motive forcepredominantly parallel to the ground (horizontal flight), the tailboomcan be orthogonal to the suspension structure, extending rearward in anorientation where it can develop pitching and yawing moments to controland stabilize horizontal flight.

In a method of the invention, a payload unit pivotally couples to a liftunit having a propulsion subsystem (e.g., a rotor) and tailboom suchthat the tailboom and payload unit are free to independently pivot withrespect to the lift unit about parallel axes. The lift unit operates inmultiple modes during the method. In a first mode, the propulsionsubsystem provides an aerial motive force that predominantly countersgravity. In other words, the force has a vertical vector that is largerthan any combination of horizontal vectors, given a normal frame ofreference with respect to the ground. During at least a portion of thisfirst mode, the tailboom latches to the payload unit in a substantiallyvertical orientation. At some point with lift provided by a fixed wing,the lift unit transitions to a second mode in which its propulsionsubsystem provides an aerial motive force that is predominantly parallelto the ground, i.e., with a smaller vertical vector than combinedhorizontal vectors. During at least a portion of this second mode, thetailboom is released from the payload unit and is allowed to pivotindependently of the payload unit. When released, the tailboom canassume the rearward-extending orientation desirable for horizontalflight.

The above summary does not include an exhaustive list of all aspects ofthe present invention. Indeed, the inventor contemplates that theinvention includes all systems and methods that can be practiced fromall suitable combinations of the various aspects summarized above, aswell as those disclosed in the detailed description below andparticularly pointed out in the claims filed with the application. Suchcombinations have particular advantages not specifically recited in theabove summary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a flying craft according to variousaspects of the present invention in transition between vertical andhorizontal modes of flight.

FIG. 2 is an exploded perspective view of the flying craft of FIG. 1.

FIG. 3 is a perspective view of the flying craft of FIG. 1 in a stowedconfiguration.

FIG. 4 is a perspective view of the flying craft of FIG. 1 in a deployedconfiguration before operation of the lift unit.

FIG. 5 is a perspective view of the flying craft of FIG. 1 duringinitial operation of the lift unit.

FIG. 6 is a perspective view of the flying craft of FIG. 1 duringoperation of the lift unit hovering above a payload to be transported.

FIG. 7 is a perspective view of the flying craft of FIG. 1 duringoperation of the lift unit in a vertical mode of flight with the payloadof FIG. 6 in transit.

FIG. 8 is a perspective view of the flying craft of FIG. 1 duringoperation of the lift unit in a horizontal mode of flight with thepayload of FIG. 6 in transit.

FIG. 9 including FIGS. 9A and 9B is a cut-away side view of a fasteneron the payload unit of the flying craft of FIG. 2 with the tailboomlatched to, and released from, the payload unit.

FIG. 10 including FIGS. 10A, 10B, and 10C, is a schematic side view ofthe flying craft of FIG. 1 during horizontal flight and two stages oftransition to vertical flight.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

A VTOL flying craft according to various aspects of the presentinvention employs a tailboom to facilitate efficient, stable flight inboth vertical and horizontal modes. As may be better understood withreference to FIG. 1, for example, one such flying craft 100 includes asuspension structure 110, a payload unit 130, and a lift unit 120 thatincludes a nacelle 128 and a tailboom 140. One end 113 of suspensionstructure 110 pivotally couples to lift unit 120 while an opposite end115 pivotally couples to payload unit 130. Lift unit 120 furtherincludes an aerodynamic lift structure 150.

A lift unit according to various aspects of the invention includes anyheavier-than air structure suitable for developing an aerial motiveforce including an upward component without exerting a correspondingforce on any external supporting structure or relying on aerostaticbuoyancy. A lift unit can develop such a force from a suitablyconfigured propulsion subsystem, an aerodynamic lift structure, or both.As illustrated in the exploded perspective view of FIG. 2, for example,lift unit 120 includes both a rotor 200 mounted on a hub 126 (whichextends from one end of nacelle 128) and an aerodynamic lift structure150.

In accordance with various aspects of the invention, a nacelle is astructure, typically having an aerodynamically streamlined outer shell,that serves as a central point of pivotal attachment between a lift unitand a suspension structure, and between a tailboom and other portions ofa lift unit. A nacelle typically includes one or more engines, agearbox, and other structure that the lift unit can employ to drive apropulsion subsystem. However, a nacelle can suitably omit some or allof such structure if desired, e.g., where the propulsion subsystememploys a rotor with tip-mounted jet engines on its blades. As usedherein, the term “nacelle” includes an overall structure consisting notjust of the outer shell that is typically but not necessarily employedfor protection and aerodynamics, but also whatever internal structure isemployed to pivotally couple the lift unit to the suspension structureand pivotally couple the tailboom to the remainder of the lift unit.

A rotor, which is a particularly advantageous type of propulsionsubsystem, can include any configuration of airfoil blades mounted on ahub in a configuration suitable for the blades to rotate on an axisabout the hub and thereby generate an aerial motive force parallel tothe axis. For example, rotor 200 consists substantially of two sets 210,220 of rotor blades. Set 210 consists of blades 212, 214, 216 while set220 consists of blades 222, 224, 226. Blade sets 210, 220 areindependently rotatable about hub 126, a configuration that permits thesets to rotate in opposite directions and thus neutralize the momentthey individually generate about the axis passing through nacelle 128and hub 126. Separate turboshaft engines in nacelle 128 drive blade sets210, 220 of rotor 200.

Any structure suitable for supporting a set of rotor blades for rotationabout an axis can be employed as a hub. For example, hub 126 includes apair of coaxial torsional shafts (not shown) and two sets 310, 320 (FIG.3) of latchable pivot couplings. Each torsional shaft couples mechanicalenergy from a gear box driven by an engine or engines (not shown) insidelift unit nacelle 128 to rotor blade sets 210, 220.

Many other types of propulsion subsystems can be suitably employed todevelop an aerial motive force including an upward component, includingthose employed by embodiments 10, 100, 200, and 1600 of commonly owned,co-pending patent application Ser. No. 09/976,348, filed Oct. 12, 2001by the same inventor as the present application, which is incorporatedby reference and referred to herein as the '348 application.

Lift structure 150 includes wing panels 152, 154, which pivotally coupleto opposite sides of a fixed central airfoil portion 141 of tailboom140. Wing panels 152, 154 include partial span flaps 155, 156 that candeploy for increased lift during transition between vertical andhorizontal modes of flight. An aerodynamic lift structure according tovarious aspects of the invention is not limited to exemplary wing panels152, 154 but can be any structure suitable for developing a significantupward aerodynamic force, as appropriate for the particular aircraft'spurposes, upon passing horizontally through a fluid medium, typicallyambient air. Examples of other aerodynamic lift structures include thoseemployed by embodiments 10, 100, 200, and 6800 of the '348 application.

Rotor 200 acts in a gyrodynamically neutral fashion while generating anaerial motive force, powered by a suitable converter of fuel (or anyother suitable source of stored energy, e.g., a battery) into mechanicalenergy. With such neutrality, an aircraft has improved pitch and yawcontrol in vertical flight. Gyrodynamic theory predicts that agyroscope, when acted upon by a moment, will move through an angulardisplacement at a right angle to the applied moment. One method toneutralize this effect is to place a second gyroscope on the same axisas the first gyroscope, with the gyroscopes spinning at the same rate inopposite directions. Employing this method, the operation of blade set220 rotating counter to blade set 210 is for practical purposesgyrodynamically neutral. Unlike a gyroscopic rotor comprised of a singleset of blades, a gyrodynamically neutral system does not distort theeffects of pitching and yawing moments. Freedom from such distortionimproves pitch and yaw control.

As may be better understood with reference to FIG. 2, tailboom 140 ofexemplary flying craft 100 pivotally couples to lift unit 120, at aboutthe midpoint of the upper side of lift unit nacelle 128, by mechanicalstructure not shown. Suitable structure for such coupling includes, forexample, a hinge at the leading edge of central airfoil 141.

Pivotal coupling between tailboom 140 and lift unit 120 is not strictlynecessary for tailboom 140 to have the desirable capability of orientingin the vertical direction for vertical flight and extending horizontallyfor horizontal flight because tailboom 140 is free to pivot (togetherwith lift unit 120) with respect to payload unit 130. However, tailboom140 is capable of various orientations with respect to rotor 200 whenpivotally coupled to lift unit 120. As illustrated in FIG. 1, forexample, tailboom 140 can extend mostly horizontal from lift unit 120when rotor 200 (FIG. 2) is oriented somewhat vertically but producing amostly horizontal air stream due to horizontal flight of craft 100.Another benefit of pivotal coupling between tailboom 140 and lift unit120 is that, as illustrated in FIGS. 3-4, nacelle 128 can be orientedvertically alongside payload unit 130 with tailboom 140 and suspensionstructure 110 oriented substantially horizontal between nacelle 128 andpayload unit 130.

Lift unit 120 includes landing gear 229 (FIG. 2) that supports lift unit120 when craft 100 is in a stowed configuration, as further discussedbelow with reference to FIG. 3. Landing gear 229 can be, e.g., a set ofwheels having sufficient dimensions and structural integrity to supportweight of lift unit 120, or a fixed structure designed to fit into amated receptacle.

A suspension structure according to various aspects of the inventionincludes any structure suitable for suspending a payload unit from alift unit. For example, suspension structure 110 includes a pair oftensile members 112, 114 that are fabricated from suitable materials(e.g., carbon graphite) in a suitable structural configuration (e.g.,extruded hollow-core piping with aerodynamic cross-section, optionallyincluding fuel pipes and mechanical and/or electrical power and controlcables) to suspend payload unit 130 and payload 190 from lift unit 120during all expected flight conditions of craft 100.

In exemplary flying craft 100, lift unit 120 couples to payload unit 130through a suspension structure 110 that is rigid. Rigidity of tensilemembers 112, 114 helps maintain structural integrity of craft 100 in itsstowed and initial deployment configurations. As discussed below, thoseconfigurations are illustrated in FIGS. 3 and 4, respectively.Suspension structures according to various aspects of the invention canhave many advantageous variations, as may be better understood withreference to paragraph 96 (yaw control) and paragraphs 104-105, 107,111-112, 128-130, and 135 (damped elastic structure) of the '348application.

Advantageously, a suspension structure of a vertical lift flying craftaccording to various aspects of the invention can pivotally couple to alift unit about one axis while being constrained from rotation about thetwo orthogonal axes. By permitting rotation about one axis andrestricting rotation about the others, such a configuration permitsmovement of a suspended payload unit within a common plane with the liftunit while preventing the payload unit from substantial lateraldeviations outside that plane. For example, bearings 127 at end 115 ofsuspension structure 110 permit fore and aft movement of payload unit130 but restrict sideways movement. Thus, the plane of permissiblemovement is parallel to the direction of horizontal flight, and flyingcraft 100 enjoys roll stability as a result.

As illustrated in FIG. 2, lift unit 120 has bearings 127 mounted onsides of its nacelle 128 that pivotally couple to the top ends of tubes112, 114. In addition, payload unit 130 includes bearings 137 thatpivotally couple to the bottom terminations of tubes 112, 114. Thus liftunit 120 suspension pivotally couples to end 115 of suspension structure110, while payload unit 130 pivotally couples to the opposite end 113 ofsuspension structure 110.

Pivoting between structural members, in accordance with various aspectsof the invention, employs any type of structure that permits axialrotation between two members while transferring lateral forces from onemember to another. One example of such structure is a conventionalbearing that includes a first member that is (or includes) at least oneshaft and a second member coupled to the first member such that theshaft is free to rotate but not move laterally with respect to thesecond member. Another example is shown as element 102 in FIG. 4 of the'348 application and accompanying text. Other types of pivot structuresinclude ball-and-socket arrangements and lengths of flexible cable.

Exemplary payload unit 130 further includes: a roof 132 with fairings131 on each side; a crew compartment 134; upper truss members 136; lowertruss members 135; a forward end cap 138; an aft end cap 139; and apayload stabilizing structure 133. The weight of a 20-foot standardcargo container is carried from the four corners of its base, throughthe lower truss members 135, to the upper truss members 136, and upthrough the suspension structure 110 (FIGS. 6-8). Crew compartment 134includes a clear canopy for pilot visibility and suitable seating,controls, and environmental comfort systems (not shown) for one or morecrew members. Truss members 135 and 136 can fold upward and intofairings 131 in the underside of roof 132 when not in use.

Some of the many possible alternative embodiments that can beconstructed and operate according to various aspects of the inventioninclude unmanned flying craft of any suitable size (e.g., smaller than atypical human), manned or unmanned flying craft dimensioned to carrymore than one cargo container as payload, flying craft configured tocarry a number of passengers, and flying craft containing a payload thatis an integral part of its payload unit or carried inside an enclosureof the payload unit.

An exemplary method for flying craft 100 to transport payload 190 may bebetter understood with reference to the sequence of FIGS. 3-4-5-6-7-1-8.

FIG. 3 illustrates flying craft 100 (with a partially cut-away view ofwing panel 152) before any flight takes place in the exemplary method.Sets 310, 320 of latchable pivot couplings are mounted between theblades of sets 210, 220, respectively, and hub 126 so that the bladescan orient parallel to tailboom 140 for the compact stowageconfiguration illustrated. In an exemplary configuration, rotor 200(FIG. 2) has a radius of about 40 ft. while tailboom 140 and suspensionstructure 110 each have a length of about 40 ft. The benefit of thesedimensions is apparent when it is noted that craft 100 rests in adiagonal “corner-to-corner” orientation on a standard naval weaponselevator 330 measuring 44 by 50 ft. Lift unit 120 rests on the supportsurface (elevator 330) alongside payload unit 130, and is held uprightby tailboom 140, which is pivotally latched to the payload unit 130.

Another benefit arises from the radius of rotor 200 being slightly lessthan the length of suspension structure 110. In that case, the rotor canadvantageously mount close to the pivotal coupling (nacelle 128). Asillustrated in FIG. 8, in that case, operating rotor 200 sweeps nearlythe largest possible area, and thus has the greatest possibleefficiency, without tips of the rotor blades hitting payload unit 130 ina horizontal mode of flight.

FIG. 4 illustrates flying craft 100 after deployment from the stowedconfiguration of FIG. 3 but with lift unit 120 not yet operational,still supported by landing gear 229 and held upright by tailboom 140.Blades 212, 214, 216 and blades 222, 224, 226 are fully deployed, theblades of each set extending equispaced about hub 126. As would beexpected for a counter-rotating coaxial rotor, blades in the two setshave opposite chord profiles, an example of which FIG. 4 illustrateswith blades 214, 220. Wing panels 152, 154 hang from their pivotalattachments to central airfoil 141 at their lowest gravitationalpotential. Payload stabilizing structure 133 is tilted rearward, readyto hang down at the back of payload unit 130 to stabilize it duringhorizontal flight.

The method of operation of flying craft 100 proceeds, as may be betterunderstood with reference to FIG. 5, with lift unit 120 moving away fromsupport surface 420 and about payload unit 130 in an arc 510 until itbegins to suspend payload unit 130. This initial motion of lift unit 120is made possible in the exemplary embodiment by pivotal coupling betweenpayload unit 130 and end 113 of suspension structure 110 and pivotalcoupling between tailboom 140 and lift unit 120. When tailboom 140 islatched to payload unit 130 during this motion, as is preferred,tailboom 140 contributes to the structural integrity of the mechanicalconnection between lift unit 120 and payload 130 as lift unit 120 movesin arc 510. (The overall structure is akin to a parallelogram.)

FIG. 6 illustrates flying craft 100 hovering above payload 190 with liftunit 120 operating in the vertical mode, generating a predominantlygravity-countering aerial motive force. Tailboom 140 is suitably latchedto payload unit 130 in a substantially vertical orientation. Thedeviation of tailboom 140 from vertical is only about five degrees inthe configuration of FIG. 6. In this configuration, tailboom 140 cancooperate with suspension structure 110 to support any forces of liftunit 120 that push down on or shear across payload 190 when craft 100descends onto it. At that point, upper support trusses 136 rotate toextend from recesses in roof 132. When payload unit 130 is to contact asensitive external load such as containerized fuel, both flying craft100 and the external load can be grounded before payload unit 130contacts the load.

In an alternative method, craft 100 can rest on or suspend from asuitable support before taking off, in a position similar to that shownin FIGS. 4-6, allowing payload 190 to be mounted on payload unit 130before craft 100 begins flight. FIGS. 27-32, 41-45, and 50-52 of the'348 application illustrate examples of such structure.

End caps 138, 139 include aerodynamic streamlining structure suitablefor the fore and aft ends, respectively, of payload 190. Any structuresuitable for decreasing wind resistance of payload 190 during horizontalflight of flying craft 100 can be employed. For example, end caps 138,139 can be fabricated from elastic sheets reinforced by internal ribs.Alternatives include inflatable structures filled with compressed airfrom an internal pump or ambient air collected in a way that exploitspressure differential between moving and still fluid bodies.

Any suitable type of fastener can be employed to latch a tailboom to apayload unit in accordance with various aspects of the invention. Such afastener can be located near the end of the tailboom, making mechanicalconnection directly to the payload unit. Alternatively, the fastener canbe at or near a pivot point between the tailboom and payload unit. Asmay be better understood with reference to FIGS. 9A and 9B, flying craft100 employs a faster 900 at the aft end of crew compartment 134 onpayload unit 130.

Fastener 900 includes an overhanging pedestal 910, which can attach withsuitable fasteners, integral construction, etc. to (1) roof 132 ofpayload unit 130 (FIG. 2) at bottom 912 of pedestal 910, or (2) the aftend of crew compartment 134 at back side 914 of pedestal 910, or (3)both. Pedestal 910 supports a cam 920 that is ratchet-mounted on a shaft930, which mounts athwart payload unit 130. Cam 920 readily movesclockwise, from the orientation illustrated in FIG. 9A (nubs extendingdownward and aft) to the orientation illustrated in FIG. 9B (nubsextending forward and downward). A ratchet (not shown) prevents cam 920from moving counterclockwise except when a suitable actuator (not shown)releases cam 920.

As illustrated FIG. 7, the bottom end of tailboom 140 includes acrosspiece 720 that connects aft ends of empennage booms 142, 144together. In latching operation of fastener 900, as illustrated in thesequence of FIGS. 9A-9B, crosspiece 720 pushes cam 920 in a clockwisedirection and secures between a downward-pointing nub of cam 920 and aninterior wall of pedestal 910. When thus secured, crosspiece 720 keepstailboom 140 latched to payload unit 130. An actuator (not shown) canrelease cam 920, under computer or operator control, to rotatecounterclockwise about shaft 930 and release tailboom 140 from payloadunit 130, thereby allowing tailboom 140 to pivot independently ofpayload unit 130.

Regardless of the particular type of fastener employed, latching thetailboom to the payload unit fixes it in an orientation substantiallyparallel to suspension structure 110. This configuration prevents thetailboom from repeatedly banging against the payload unit during lateralmovements of the flying craft. It also permits suspension structure 110and tailboom to mechanically cooperate in supporting forces of the liftunit when the tailboom is resting on a surface. Furthermore, with aforward center of gravity in payload 190, pivotally latched tail 140 ispushed up towards lift unit 120. A limit on forward center of gravity ofan acceptable payload can be imposed to assure sufficient rotor pitch-upcontrol authority in vertical flight mode, balancing the nose-downmoment produced by pivotally latched tailboom 140.

When the tailboom is not latched to the payload unit, it can be leftfree to rotate, within an angular range, about a rotational axis that isorthogonal to an axis passing through the first and second ends ofsuspension structure 110. Exemplary lift unit 120 includes an actuator(not shown) that is coupled via tilt boom 143 to pivot tailboom 140 withrespect to nacelle 128. As may be better understood with reference toFIGS. 11-13. Another benefit of pivotal coupling between tailboom 140and lift unit 120, discussed below with reference to the sequence ofFIGS. 10A-10B-10C, is that an actuator (not shown) at the couple caneffect tilt of rotor 120 and initiate a transition from horizontal tovertical flight.

As discussed above with reference to FIG. 10C, flying craft 100 can movehorizontally even in a vertical mode of flight, though not with theefficiency and speed of horizontal flight mode. For example, FIG. 7illustrates flying craft 100 in a vertical mode of flight with payload190 attached to payload unit 130, and with craft 100 moving horizontallyat a modest speed. During the vertical mode of flight, tailboom 140 canhang from lift unit 120 in an orientation substantially parallel tosuspension structure 110, as illustrated in FIG. 6. This configurationminimizes resistance to downwash from lift unit 120.

Payload stabilizing structure 133 hangs down at the aft end of payloadunit 130, in a position to interact with an airstream resulting fromforward motion of craft 100 (represented by arrow 710) and thusstabilize pitch and yaw of payload unit 130, e.g., as discussed below.The airstream also pushes back (a) tailboom 140, which at this point mayfreely pivot with respect to payload unit 130, and (b) wing panels 152,154 of aerodynamic lift structure 150, which thus begin to assume anoperating position extending substantially orthogonal from tailboom 140.Advantageously, no actuator is needed to move wing panels 152, 154 intoposition, though one can be employed if desired.

FIG. 1 illustrates flying craft 100 during transition between thevertical mode of flight illustrated in FIG. 7 and the horizontal mode offlight illustrated in FIG. 8. At this point, aerodynamic lift structure150 is fully in its operating position and is developing a substantialportion of the lifting force generated by lift unit 120. In a particularexample, horizontal speed at transition is about 122 knots.

FIG. 8 illustrates flying craft 100 in a fully horizontal mode offlight. In this mode, aerodynamic lift structure 150 efficientlygenerates most of the lifting force from lift unit 120 to keep craft 100airborne. Except for minor upward force from any slight upward pitch oflift unit 120, rotor 200 serves strictly as a horizontal propulsiondevice to (a) pull aerodynamic lift structure 150 through the air sothat structure 150 can generate lift and (b) move flying craft 100 toits destination. In a particular example, horizontal speed in horizontalflight mode is about 312 knots.

As discussed above, lift unit 120 couples to suspension structure 110pivotally around bearings (not shown) at upper end 115 of suspensionstructure 110. Consequently, lift unit 120 can assume either a verticalor horizontal orientation. Flying craft 100 can thus operate in avertical mode of flight in which lift unit 120 generates a verticalaerial motive force predominantly opposing gravity, or a horizontal modeof flight in which lift unit 120 generates an aerial motive forcepredominantly parallel to the ground. FIG. 1 illustrates flying craft100 in a transition between the two modes.

During the vertical mode of flight, tailboom 140 can be substantiallyorthogonal to suspension structure 110, as illustrated in FIG. 8. Inthat configuration, tailboom 140 extends rearward in an orientationwhere it can develop pitching and yawing moments to control andstabilize horizontal flight and where it can counteract a momentproduced by aerodynamic lift structure 150.

A tailboom according to various aspects of the invention includes anystructure suitable for interacting with an airstream at one end todevelop a moment about an opposite end. Interaction with an airstreamcan take place passively, with movable control surfaces or fixedairfoils. Alternatively or in addition, airstream interaction can employone or more active generators of aerial motive force, e.g., a tailrotor. As may be better understood with reference to FIG. 2, forexample, tailboom 140 is of a type that employs vertical stabilizerswith rudders and a horizontal tail to passively interact with anairstream, which results from downwash produced by rotor 200 orhorizontal flight of craft 100, or both.

A control surface according to various aspects of the invention includesany stabilizer, aileron, elevator, rudder, tail, or trimming device thatcan be suitably employed to influence roll, pitch, or yaw of a flyingcraft. For example, tailboom 140 includes vertical stabilizers 146, 148with rudders 145, 147 and a horizontal tail 149 mounted atop verticalstabilizers 146, 148. Tail 149 has an elevator 410 (FIG. 4) with a 30%chord partially spanning it. Tailboom 140 further includes two empennagebooms 142 (FIG. 2) and 144 (FIG. 4) to which vertical stabilizers 146,148, respectively, are attached.

The operation of tailboom 140 to counteract moment produced byaerodynamic lift structure 150 may be better understood with referenceto FIG. 8, which illustrates flying craft 100 in horizontal flight.Wings 152, 154 of aerodynamic lift structure 150 (best seen in FIG. 2)generate lift due to forward motion of craft 100, which results fromaerial motive force from lift unit 120 that is predominantly parallel tothe ground (not shown). As with the aerial motive force that lift unit120 generates in hover, lifting force from aerodynamic lift structure150 can be viewed as a vertical vector 810 passing through a pointherein called the “center of lift.” This point is displaced slightly aftof end 115 of suspension structure 110, where lift unit 120 pivotallycouples to suspension structure 110.

The weight of payload unit 130 with captured payload 190 imparts adownward force 820 on suspension structure 110, which lifting force fromaerodynamic lift structure 150 opposes to keep craft 100 airborne. Thehorizontal displacement between the center of lift from structure 150and the pivot point of end 115 of suspension structure 110 results in amoment 830 about the point, which acts to pitch craft 100 downward.

Elevator 410, located on horizontal tail 149 of tailboom 140 andillustrated in FIG. 4, can orient slightly upward or downward (e.g.,plus or minus 20 degrees) with respect to tail 149. To counteract thedownward-pitching moment from aerodynamic lift structure 150, elevator410 can orient upward and interact with the airstream resulting fromforward motion of craft 100 to develop an opposing, upward-pitchingmoment 840.

As may be better understood with reference to the sequence of FIGS.10A-10B-10C, flying craft 100 can employ an actuator (not shown) at thepivotal couple (not shown) between tailboom 140 and nacelle 128 to tiltrotor 200 and transition from a horizontal mode of flight (as in FIGS.8, 10A) to a vertical mode of flight with some horizontal velocity (asin FIGS. 7, 10C). During the horizontal mode of flight (FIG. 10A), tail149 of tailboom 140 advantageously interacts with the airstream fromhorizontal motion of flying craft 100 to counteract a downward-pitchingmoment from aerodynamic lift structure 150 with an upward-pitchingmoment of its own, as discussed above.

To initiate a transition to vertical flight mode, the actuator applies acounterclockwise (from the observer of FIG. 10B′sperspective) moment totailboom 140 relative to nacelle 128 while elevator 410 (FIG. 4) adjustsslightly to increase its upward-pitching moment. The result is thattailboom 140 maintains its orientation with respect to the ground (notshown) and nacelle 128 rotates clockwise with respect to tailboom 140,bringing rotor 200 into a vertical orientation. As illustrated in FIG.10C, flying craft 100 can move in a horizontal direction in verticalflight mode with rotor 200 tilted slightly forward and tailboom 140trailing behind where tail 149 can influence pitch and rudders 145, 147(FIG. 2) can influence yaw.

In the schematic view of FIG. 10, nacelle 128 can also be understood asthe center of gravity of craft 100. The aerial motive force normal tothe plane of rotor 200 passes through this center of gravity. Nacelle128 is preferably locked under aerodynamic lift structure 150 when wingpanels 152, 154 (FIG. 2) are at 10% mean aerodynamic chord.

Advantageously, payload unit 130 imparts lateral stability to flyingcraft 100 by suspending from lift unit 120 with rotation restrictedabout one axis. In this suspended configuration, payload 190 increasesthe moment of inertia in the plane that includes parallel members 112,114 (FIG. 2). As a result, suspended payload 190 increases stabilityabout the axis normal to that plane.

The force of gravity tends to position payload unit 130 beneath liftunit 120, which lowers the center of gravity and increases pendularstability. This behavior conforms to accepted aircraft design theory,which holds that pendular stability (also known as lateral stability orroll stability) increases for “high wing” airplanes having a low centerof gravity. Contrary to some conventional teachings, enhancement ofpitch stability of lift unit 120 is not primarily due to the addition ofsuspension structure 110 and payload unit 130. Instead, the mass ofpayload unit 130 is believed to behave in pitch like a point mass at theaxis of rotation. Pitch stability and control of lift unit 120 are thusunaffected by the addition of suspension structure 110 and payload unit130, while roll or pendular stability in horizontal flight (FIG. 9) andyaw stability in vertical flight (FIG. 8) increase.

Various particular features of exemplary flying craft 100 may be betterunderstood with reference to the labeled paragraphs below. In variationswhere the benefits of these particular features are not required, theymay be suitably omitted or modified while retaining the benefits of thevarious aspects of the invention discussed above. With possibleexceptions, structural elements not introduced with a reference numeralare not illustrated in the drawings. Those structural featuresreferenced by number are illustrated in FIG. 2 unless otherwiseindicated.

PAYLOAD UNIT—Payload unit 130 is optimized to capture and streamlineexemplary payload 190, which is a 20-foot MILVAN container. Payload unit130 can be reconfigured in flight to capture and partially streamline a40-foot ISO container. A winch is located below crew compartment 134 forattaching slung cargo. A special MILVAN with containerized fuel, fuelpump, and streamlined bottom can be provided for a self-deploymentferrying operation. The aircraft portion of a recovery assist system islocated on either side of payload unit 130 at suspension structure 110attachment points. Payload unit 130 may also be operated without havingan external load.

CREW COMPARTMENT—Crew compartment 134 holds one pilot, having dimensionsof 4 foot height, 4 foot depth, and 3 foot width. The entire monocoquecrew compartment is mounted to payload unit 130 by oleo struts for shockabsorption upon landing, and can be jettisoned for emergency egressincluding parachute recovery with positive buoyancy for ocean recovery.Crew compartment 134 then becomes a self-contained recovery module.Provisions for a remote co-pilot are also provided.

GENERAL FLIGHT CONTROLS—Flying craft 100 permits single pilot operationfrom either crew compartment 134 or a remote operator's console. Controlmoments are generated by means of rotor and fixed surface controls, withrotor cyclic control phased out as craft 100 converts from a vertical toa horizontal mode of flight. The conversion and power management systemsare designed for straightforward cockpit procedures. All normal andemergency procedures can be controlled by a single pilot.

COCKPIT CONTROLS—The cockpit controls include a longitudinal/lateralstick, a collective-type power lever, and pedals for both the pilot andthe remote operator. The throttles contain levers that control flaps155, 156 and a blade-pitch governor hand-wheel for manual override ofthe rotor governor. A three-position switch on the power lever controlsthe nacelle conversion angle.

ROTOR CONTROLS—In vertical flight mode, pitching moments arise fromapplication of longitudinal cyclic pitch change to blades of rotor 200,and rolling moments from applying lateral cyclic pitch change. Upward ordownward movement of the power lever simultaneously increases ordecreases engine power and rotor blade collective pitch to providevertical thrust control. Differential rotor collective pitch generatesyawing moments in vertical flight mode and rolling moments in horizontalflight mode.

FIXED CONTROLS—Elevator 410 (FIG. 4) is active in all flight modes.During conversion from a vertical to a horizontal mode of flight, thedesired control response is achieved by phasing out the cyclic pitchcontrol as aerodynamic lift structure 150 offloads the rotor, and byphasing differential collective from pedal control to the lateral stickcontrol. Wing panels 152, 154 have partial span flaps 155, 156,respectively, for increased lift during conversion.

FLIGHT MODE CONVERSION—The conversion system is mounted to the gearboxand active only during conversion between vertical and horizontal flightmodes. The system engages with tilt boom 143 to pull nacelle 128underneath aerodynamic lift structure 150 for horizontal mode, or togradually release nacelle 128 for vertical mode. The force is providedby redundant linear actuators having hydraulic motors andelectrically-powered servo valves. The conversion system disengages withtilt boom 143 when not active. In the event of conversion systemfailure, an automatic mechanical damper temporarily engages with tiltboom 143 to modulate movement of nacelle 128 into vertical mode.

POWER MANAGEMENT—A power management cockpit control consists of a pairof throttles and a power lever. The collective stick-type power leversare located to the left of the pilot and have the same sense of motionas a conventional helicopter collective stick. Following engine startand checkout, each throttle lever is hooked to the power lever. Then, invertical flight mode, power lever motion simultaneously changes thepower setting of the rotors. In horizontal flight mode, however, thepower lever only controls power setting of the engines as the collectivepitch input is phased out as a function of nacelle tilt angle. Inaddition, power management is simplified by the automatic inputs of arotor collective pitch governor which adjusts to maintain the rotor rpmselected by the pilot.

POWER PLANT—Two Rolls-Royce AE 1107 turboshaft engines and a co-axialgearbox are located in nacelle 128, which is of the centerline type. Theco-axial gearbox provides function similar to the gearbox in the KamovKa-32A helicopter. Total engine rating is 12,300 HP and transmissionrating is 10,209 HP.

PAYLOAD UNIT YAW STABILIZATION SUBSYSTEM—Yawing sensors are mounted tosuspension structure 110 to provide control information. A feedback loopconverts yawing strain on suspension structure 110 into a correctingmoment at rudders of payload stabilizing structure 133, thereby aligningpayload unit 130 with lift unit 120 and preventing yaw divergence. Thepilot may override the yaw stabilization subsystem with pedal control,or disable it at lower airspeeds with well-behaved external loads.

LIFT UNIT GUST AND LOAD ALLEVIATION SYSTEM—During ground modeoperations, lift unit 120 is automatically controlled to minimize stresson latched tailboom 140. Strain sensors mounted on payload unit 130 atthe latching fastener measure roll and yaw moments exerted by payloadunit 130 on tailboom 140. A feedback loop to the rotor controls createsan equivalent moment at rotor 200, releasing strain from tailboom 140.For high sea states with a rolling deck, rotor 200 follows the rotationof grounded payload unit 130 without stressing tailboom 140. The pilotmay disable lift unit 120 gust and load alleviation system for lightexternal loads, or for calm air with a stable deck.

ROTOR RPM GOVERNOR—The rotor RPM governor can be used in all modes tosimplify power management. It is a closed loop system that maintains apilot-selected RPM by controlling collective blade pitch. In verticalflight mode, the collective pitch inputs from the RPM governor aresuperimposed on the collective pitch inputs from the power lever and thedifferential collective pitch inputs from the control stick. Inhorizontal flight mode, the primary collective pitch input comes fromthe RPM governor as required to maintain pilot selected RPM. Thisresults from the fact that during transition the collective pitch inputsfrom the power lever are phased out, and only a small amount ofdifferential collective pitch inputs from the control stick are retainedin horizontal flight mode for roll control. The pilot can manuallyoverride the RPM governor.

FUEL SYSTEM—Fuel is supplied to the engines by a lightweight, crashresistant, 4,000 pound capacity fuel cell contained in fixed centralairfoil portion 141. Gravity refueling is accomplished through a fillercap. External fuel is supplied by a special 24,000 pound fuel capacityMILVAN shaped container. Redundant, electrically driven boost pumpslocated at the lowest point of the container deliver fuel up through ahose in the left side of suspension structure 110 to a fuel cell inengine nacelle 128. Alternatively, fuel may be pumped using ambient aircollected in a way that exploits pressure differential between movingand still fluid bodies. The interface between the special MILVAN andpayload unit 130 has quick release fuel connections and quick releaseelectrical connections. The hose in suspension structure 110 haspivoting connections on both ends to allow free pivotal movement atnacelle 128 and at payload unit 130.

HYDRAULIC SYSTEM—Flying craft 100 has three independent transmissiondriven hydraulic systems. The pump for each system is geared to therotor side of the transmission clutch so that full hydraulic power canbe provided with both engines shut down, as long as the rotors areturning within the normal speed range. The hydraulic systems power thecyclic control, collective control, RPM governor, elevator, and heatexchanger blower.

ELECTRICAL SYSTEM—The electrical system consists of dual DC and ACelectrical subsystems with sufficient capacity to accommodate peak loadrequirements with one engine out. A battery is connected to each DC busduring normal operation. The batteries provide self-containedengine-start capability. DC power is delivered to payload unit 130through a distribution bus within the right side of suspension structure110. AC power at payload unit 130 is supplied by two solid-stateinverters.

ENVIRONMENTAL CONTROL SYSTEM—The environmental control system providesheating, ventilation, air conditioning, window defogging, and crewbreathing oxygen for crew compartment 134. Heating is provided byelectric powered heaters. An ambient air-inlet valve enables theintroduction of unconditioned air for fresh air ventilation of crewcompartment 134. An electrically powered inlet fan provides the requiredairflow at all flight conditions. Noise and vibration control structureor equipment can be included as desired.

MONOCOQUE STRUCTURES—Wing panels 152, 154, vertical stabilizers 146,148, rudders 145, 147, horizontal tail 149, elevator 410 (FIG. 4), andpayload stabilizing structure 133, and crew compartment 134 are ofconventional monocoque construction. Booms 142, 143, 144 are made ofrigid tubular metal. Suspension structure 110 is made of high tensilestrength composites. Payload unit 130 has high tensile strength upperand lower truss members 136, 135 for holding payload 190 (FIG. 6) andlightweight aerodynamic end caps 138, 139 for enveloping payload 190 ina streamlined shape.

LANDING GEAR—Payload 190 provides its own landing gear. When no load isattached, payload unit 130 supports itself without any special landinggear requirements. Nacelle 128 includes biped landing gear 127 whichprovides support in rest mode and absorbs shocks in the event of gustsor deck movement while near rest mode. Each leg is rated to support15,000 pounds.

TAIL BOOM AND SUSPENSION STRUCTURE LATCHES—During ground mode andvertical flight mode, tailboom 140 is latched to payload unit 130 atfastener 910 (FIGS. 9A, 9B). Transition to forward flight, i.e.,horizontal flight mode, begins with shaft 720 released from fastener 910and tailboom 140 free to rotate with the airstream. When not engaged,fastener 910 reverts to a capture state, as illustrated in FIG. 9A. Inthe reverse transition from horizontal to vertical flight mode, fastener910 recaptures tailboom 140. Suspension structure 110 can freely pivotwith respect to payload unit 130 at bearings 137 (FIG. 2), but its anglewith respect to payload unit 130 can be fixed when shaft 720 is releasedand freed again when the tail latching engages.

PAYLOAD UNIT—Payload unit 130 is comprised of load carrying members andaerodynamic members. Pivoting support trusses 136, 136 carry the loadfrom the lower corners of the ISO container (payload 190 of FIG. 6) tosuspension structure 110. The aerodynamic members are the roof 132,payload stabilizing structure 133, sides, and end caps 138, 139. Endcaps 138, 139 have a pivotal attachment to the lower end of lower trussmembers 135, and a screw jack attachment to roof 132. As the screw jackrotates, the end cap translates over the roof edge and rotates uppersupport truss members 136. Each one of end caps 138, 139 has latches forholding the ISO container corners. The jack screws and latches areelectrically actuated. Accordion siding can unfold with the rotatingsupport truss members 136. In operation (FIG. 6), flying craft invertical flight mode lowers payload unit 130 onto payload 190. Then thescrew jacks rotate to lower end caps 138, 139, truss members 135, 136,and siding onto payload 190. Latches hold end caps 138, 139 and members136 to the corners of the ISO container. After the container is secure,craft 100 lifts and transitions to cruise, i.e., horizontal flight mode(FIG. 8), as end caps 138, 139 inflate to a streamlined shape. Flyingcraft 100 carries payload 190 to its destination and reverses theoperation to release payload 190 and rotate end caps 138, 139 into ahorizontal position for the return flight. Payload unit 130 may bereconfigured in flight to accommodate either a 20-foot or a 40-foot ISOcontainer. Truss members 135 and 136 overlap one another may be extendedor retracted in flight. For oversize load operations, a cargo net may besnugged up to the payload unit 130 by the integrated wench. The aircraftportion of the recovery assist system deploys two messenger cables fromeither side of payload unit 130 at end 113 of suspension structure 110(attachment points) for recovery onto a container or down to the deck ofa ship. Flying craft 100 may self-deploy using a special streamlinedMILVAN fuel container.

ROTOR—Disk area of rotor 200 is 5,026 square feet. In vertical flightmode, the rotor disk plane is parallel with the roof 132 of payload unit130. In horizontal flight mode, the rotor centerline is fixed at 10degrees below centerline of aerodynamic lift structure 150, thusproviding axial thrust with wing panels 152, 154 near maximum liftcoefficient. In horizontal flight, the tips of blades in sets 210, 220should clear payload unit 130 by about 1.5 feet. The tips of blades inset 210 and should clear wing panels 152, 154 by about nine feet.

STRUCTURAL CONFIGURATION AND MATERIALS—The entire craft (again, only ina particular embodiment) has a maximum gross weight of about 74,000pounds. Three important structural components are the booms 142, 143,144, tailboom 140 as a whole, and suspension structure 110. Tailboom 140provides structural support during take-off and landing. Duringtransition from rest mode to grounded vertical flight mode, tailboom 140is latched to payload unit 130. Suspension structure 110 providestensile support in opposition to the compressive support of tailboom140, which together form a rigid cantilever arm about the roll axis toabsorb rolling and yawing moments due to wind gusts or ship deckmovement. Suspension structure 110 provides sufficient tensile strengthto support a 37,000 pound payload in vertical flight mode at 150 knots,and support a 30,000 pound payload in horizontal flight mode at 350knots with appropriate safety margin. The tilt boom has sufficienttensile strength to pull the gearbox underneath the wing duringtransition to horizontal flight mode, and sufficient rigidity incombination with the booms 142, 143, 144 to prevent rotor whirl-inducedtail flutter. Payload unit 130 has trusses 135, 136 of sufficienttensile strength to hold a 40-foot ISO container weighing 37,000 pounds,and sufficient toughness to withstand the impact of lowering thecontainer onto a sea state 5 deck. In horizontal flight mode, fixedcentral airfoil portion 141 locks down to both the gearbox and foldingwing panels 152, 154 for increased structural integrity.

AUTOROTATION—Rotor 200 has low disk loading and thus can be operated inautorotation mode for reduced descent rate emergency landing. In theevent that all power is lost, flying craft 100 can automatically revertto autorotation mode. Blades 212-226 of rotor 200 revert to autorotationpitch, a failsafe conversion damper engages, locks of wing panels 152,154 release, and elevator 410 (FIG. 4) rotates up. The oleo strutssupporting crew compartment 134 and supporting biped landing gear 127can be fabricated to withstand the autorotation sink rate at designgross weight.

ENGINE SAFETY—Blade sets 210, 220 are driven by center mounted enginesof proven high reliability. A co-axial gearbox connecting the pair ofengines to the pair of blade sets 210, 220 allows either engine to powerboth blade sets in the event of an engine failure. Overrunning clutchesin the engine speed reduction gearing can automatically disconnect afailed engine from the drive system, thus allowing the effective use ofavailable power. Single engine performance, stability, and control aresimilar to two engine operation at low power settings because of theco-axial gearbox in nacelle 128. Horizontal flight mode and transitioncan be performed as normal, but single engine hover (vertical flightmode) is then limited to low payload weights. The conversion mechanismis simple and engages natural aerodynamic forces. In the event ofcomplete loss of power, conversion from horizontal to vertical flightmode with autorotation is automatically achieved.

SYSTEM SAFETY—Appropriate levels of hydraulic system and electricalsystem redundancy and safety are included in the design of the aircraft.A pilot caution and warning system can provide visual and/or audibleindications of detectable system malfunctions, such as hydraulic systempressure loss, rotor control discrepancies, engine fire, latch failure,etc. Instrumentation will be incorporated to monitor loads and positionsat critical locations (such as control linkages, control surfaces, etc.)during flight.

Other particular features of exemplary flying craft 100 and variationsin the better understood with reference to the contents ofwww.baldwintechnology.com, which is incorporated herein by reference.

PUBLIC NOTICE REGARDING THE SCOPE OF THE INVENTION AND CLAIMS

The inventor considers various elements of the aspects and methodsrecited in the claims filed with the application as advantageous,perhaps even critical to certain implementations of the invention.However, the inventor regards no particular element as being“essential,” except as set forth expressly in any particular claim. Forexample, a claim calling for an aerodynamic lift structure but not forpivotally coupled wing panels reads on flying craft employing anysuitable type of aerodynamic lift structure (e.g., single fixed wing,fabric free wing) regardless of whether the system employs such wingpanels or not.

While the invention has been described in terms of preferred embodimentsand generally associated methods, the inventor contemplates thatalterations and permutations of the preferred embodiments and methodswill become apparent to those skilled in the art upon a reading of thespecification and a study of the drawings. For example, a hub employinga pair of blade pitch control rods surrounding a central shaft, or otheropen structure, can substitute for hub 126 of FIG. 2.

Additional structure can be included, or additional processes performed,while still practicing various aspects of the invention claimed withoutreference to such structure or processes. For example, a rotor can be ofa “variable geometry” type that works well in both vertical andhorizontal modes of flight, as disclosed in published U.S. patentapplication Serial No. 2002/0098087 filed Jan. 23, 2001 by Yuriy and inU.S. Pat. No. 6,019,578 issued Feb. 1, 2000 to Hager et al. and U.S.Pat. No. 6,578,793 issued Jun. 17, 2003 to Byrnes et al., all of whichare incorporated herein by reference. (Patents and patent applicationsincorporated herein by reference may themselves incorporate documents byreference, and such documents are also incorporated herein byreference.) Another example of a “variable geometry” rotor employsblades having multi-element airfoils. The blades include flaps that canextend from to increase surface area during slower vertical-modeoperation and retract to permit efficient high-velocity operation inhorizontal flight mode, where the rotor is called upon to generateefficient axial thrust. Furthermore, wing panels 152, 154 may be removedto lighten the lift unit and increase payload weight for short haulflights in vertical flight mode.

Accordingly, neither the above description of preferred exemplaryembodiments nor the abstract defines or constrains the invention.Rather, the issued claims variously define the invention. Each variationof the invention is limited only by the recited limitations of itsrespective claim, and equivalents thereof, without limitation by otherterms not present in the claim.

In addition, aspects of the invention are particularly pointed out inthe claims using terminology that the inventor regards as having itsbroadest reasonable interpretation; the more specific interpretations of35 U.S.C. § 112(6) are only intended in those instances where the terms“means” or “steps” are actually recited. For example, the term “ground”is broadly used herein to indicate a portion of the earth's surface (or,conceivably, the surface of an extraterrestrial body) that is beneath aflying craft, regardless of whether the surface is actually dry land ora body of water. As another example, the term “orthogonal” is used toindicate that two structures are oriented substantially 90° from eachother, without requiring an exactly perpendicular orientation orintersection of any axes of the structures.

The words “comprising,” “including,” and “having” are intended asopen-ended terminology, with the same meaning as if the phrase “atleast” were appended after each instance thereof. A clause using theterm “whereby” merely states the result of the limitations in any claimin which it may appear and does not set forth an additional limitationtherein. Both in the claims and in the description above, theconjunction “cr” between alternative elements means “and/or,” and thusdoes not imply that the elements are mutually exclusive unless contextor a specific statement indicates otherwise.

1-21. (canceled)
 22. A method comprising: (a) providing a lift unitincluding a propulsion subsystem and a tailboom; (b) providing a payloadunit pivotally coupled to the lift unit such that the tailboom andpayload unit are free to independently pivot with respect to each otherabout a first axis; (c) operating the lift unit in a first mode whereinits propulsion subsystem provides an aerial motive force predominantlycountering gravity; (d) during at least a portion of the first mode,latching the tailboom to the payload unit in a substantially verticalorientation; (e) transitioning the lift unit to a second mode whereinits propulsion subsystem provides an aerial motive force predominantlyparallel to the ground; and (f) during at least a portion of the secondmode, releasing the tailboom from the payload unit, thereby allowing itto pivot independently of the payload unit.
 23. The method of claim 22wherein providing the lift unit comprises providing a rotor as thepropulsion subsystem.
 24. The method of claim 23 wherein: (a) providingthe lift unit comprises providing a pair of blade sets as the rotor; and(b) operating the lift unit comprises rotating the blades of one set inan opposite direction to blades of the other set.
 25. The method ofclaim 23 further comprising, before operating the lift unit in the firstmode, resting the lift unit on a support surface alongside the payloadunit.
 26. The method of claim 25 wherein: (a) the lift unit is pivotallycoupled to the payload unit through a rigid suspension structure; and(b) the method further comprises, at the beginning of the first mode,moving the lift unit away from the support surface and about the payloadunit in an arc until it begins to suspend the payload unit.
 27. Themethod of claim 26 further comprising: (a) providing a pair of wingpanels pivotally coupled to the tailboom; and (b) before moving the liftunit, unfolding the wing panels from (1) a stowed position substantiallyparallel to the tailboom to (2) a deployed position extendingsubstantially orthogonal from the tailboom.
 28. The method of claim 23wherein suspending the payload further comprises constraining thepayload from pivotal movement about all axes orthogonal to a first axis.29. The method of claim 23 further comprising, before operating the liftunit, resting the payload unit on a surface with the tailboom latchedthereto, wherein the lift unit is at least partially supported by thetailboom.
 30. The method of claim 23 wherein releasing the tailboomincludes permitting rotation of the tailboom, within an angular range,about a rotational axis orthogonal to an axis passing between the liftunit and the payload unit.
 31. The method of claim 30 furthercomprising, after releasing the tailboom, pivotally driving the tailboomwith respect to the lift unit.
 32. The method of claim 30 furthercomprising, after releasing the tailboom, controlling pitch of thetailboom with a horizontal stabilizer and an elevator.
 33. The method ofclaim 30 further comprising, after releasing the tailboom, controllingyaw of the tailboom with a vertical stabilizer and a rudder.
 34. Themethod of claim 23 wherein providing the lift unit further comprisesproviding a pair of wing panels pivotally coupled to the tailboom, themethod further comprising: (a) while the tailboom is latched to thepayload unit, having the wing panels oriented substantially parallel tothe tailboom; and (b) while the the tailboom is released from thepayload unit, having the wing panels extending substantially orthogonalfrom the tailboom.
 35. The method of claim 23 further comprising: (a)permitting the lift unit to freely rotate, within at least apredetermined angular range, about a rotational axis orthogonal to anaxis passing through the first and second ends of the suspensionstructure; and (b) substantially constraining the lift unit frommovement relative to the first end of the suspension structure in adirection parallel to the rotational axis. 36-37. (canceled)
 38. Amethod comprising: (a) in a flying craft having a tailboom and a payloadsupport structure free to pivot with respect to each other about a firstaxis, generating an aerial motive force predominantly counteringgravity; (b) during at least a portion of part (a), having the tailboomlatched to the payload support structure, thereby arranging the tailboomin a substantially vertical orientation; (c) in the flying craft,generating an aerial motive force predominantly parallel to the ground;and (d) during a transition between parts (a) and (c), releasing thetailboom from the payload support structure, thereby allowing thetailboom and the payload support structure to pivot independently ofeach other about the first axis.
 39. The method of claim 38 wherein,when not latched to the payload support structure, the tailboom is freeto pivot about the first axis and only the first axis.
 40. The method ofclaim 38 wherein generating the aerial motive force comprises operatingat least one rotor of a lift unit to which the tailboom and the payloadsupport structure are both attached.
 41. The method of claim 38 whereinreleasing the tailboom includes permitting the tailboom to rotate aboutthe first axis, but only within an predetermined angular range.
 42. Amethod comprising, in a flying craft having a tailboom and a payloadunit free to pivot with respect to each other about a first axis and aplurality of airfoil blades held by a central hub and moveable between astowed position and a deployed position: (a) spreading the blades toform a pair of rotors coaxial with each other and a second axisperpendicular to the first axis; (b) orienting the hub in asubstantially vertical direction and rotating the rotors in oppositedirections about the second axis, thereby generating an aerial motiveforce predominantly countering gravity; (c) during at least a portion ofpart (b), keeping the tailboom lached to the payload unit, therebyarranging the tailboom in a substantially vertical orientation; (d)transitioning the hub to being oriented in a direction predominantlyparallel to the ground while continuing to rotate the rotors in oppositedirections; and (e) during part (d), releasing the tailboom from thepayload unit, thereby allowing the tailboom and the payload unit topivot independently of each other about the first axis.
 43. The methodof claim 42 wherein: (a) when not latched to the payload unit, thetailboom is free to pivot about the first axis and only the first axis;and (b) releasing the tailboom includes permitting the tailboom torotate about the first axis, but only within a predetermined angularrange.